Surfboard fins and surfboard using same

ABSTRACT

A fin for a surfboard or other waterboard with an angled winglet on the tip of the fin. The fin may be angled from the bottom of the board. A pair of fins with mirror image shapes on a surfboard with winglets on the tips of the fins angled outward away from the center of the board.

BACKGROUND

1. Field of the Invention

This invention relates to a shaped fin and to a fin and watersports board system.

2. Description of Related Art

Surfboards and wind surfing boards typically use one or more fins which may extend below the bottom of the surface of the board. The fin or fins are generally geared towards stabilization of the board in the horizontal direction while riding the board on a wave or through the water.

Detachable surfboard fins have been used for a variety of reasons, including ease of finishing the surfboard before the otherwise interfering fins are installed, and replacing damaged fins without having to repair or replace the surfboard itself. Surfboards today commonly use one, two, three, or four fins. The three fin setup usually uses a center fin and a matched pair of mirror image shaped side fins, whereas a four fin setup usually uses a two pairs of matched mirror image side fins, wherein in one pair is closer to the surfboard centerline than the other.

A typical fin mounting system for a surfboard includes a box which is embedded within the surfboard. A separate fin is then inserted into the box. The fin or fins may be adjustable longitudinally and may affixed into a number of different positions.

SUMMARY

A fin for a surfboard or other waterboard with an angled winglet on the tip of the fin. The fin may be angled from the bottom of the board. A pair of fins with mirror image shapes on a surfboard with winglets on the tips of the fins angled outward away from the center of the board.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sketch of a surfboard according to some embodiments of the present invention.

FIG. 2 is a sketch of a side view of a fin according to some elements of the present invention.

FIG. 3 is a sketch of an end view of a fin according to some elements of the present invention.

FIG. 4 is an illustrative cutaway view of a fin according to some elements of the present invention.

FIG. 5 is a rear view of a surfboard according to some embodiments of the present invention.

DETAILED DESCRIPTION

In some embodiments of the present invention, as seen in FIG. 1, board and fin system 10 consists of a board element 11 with a center fin 14 and a pair of side fins 12, 13. The side fins 12, 13 are seen with tip winglets 20, 30 on the end of the fins. In some embodiments, there may be two or more pairs of side fins. In some embodiments, there may be no center fin. Fins assist in the turning of a surfboard or other water board. Without fins, the rear end of the surfboard is likely to slip out of the surface of the water during turning maneuvers, especially during maneuvers on the steep face of a wave or while making sharp turns. Fin design often involves a tradeoff between the size of the fin, and the amount of resistance to the slipping out of the tail of the surfboard that the fin size offers, and the drag imparted upon the board by the fin. Low resistance to forward motion while offering a good “grip” of the board to the water surface is commonly sought as a design goal.

FIGS. 2 and 3 illustrate a fin 12 according to some embodiments of the present invention. A fin body element 41 constitutes most of the fin 12. The fin body element 41 has a leading edge 17 and a trailing edge 18. At the first end 15 of the fin body element 41 is a fin base portion 16 adapted to be removably attached to a mating structure on the bottom of a surfboard or other board. In some embodiments, the fin base portion 16 is adapted to snap into a receptacle that may be affixed into the bottom of the surfboard. Although a particular shape of fin base portion 16 is illustrated, different configurations of base portions may be used. In some embodiments, the fins may affixed more permanently into the bottom of the surfboard, such as by being attached as part of the fiberglassing of a fiberglass coated surfboard, for example.

The fin body element 41 has a first side 21 facing a first direction and a second side 22 facing a second direction. A tip winglet 20 is attached at a first end to a second end 19 to the fin body element 41. The tip winglet 20 angled out in the direction that the first side 21 of the fin body element 41 faces. The tip winglet may be angled in the range of 30-50 degrees from the fin body element in some embodiments.

In some embodiments of the present invention, as seen in FIGS. 1 and 5, the center fin 14 is typically mounted along the center line 14 of the bottom of the board element 11. A pair of fins, referred to here as side fins, are placed on the bottom of the board element. A first fin 12 may be placed on a first side of the centerline of the board, and a second fin 13 may be placed on a second side of the centerline of the board. The tip winglets 20, 30 will be angled from the fin body elements in a direction away from the center line of the bottom of the board element.

In some embodiments, the fin body elements will also be angled in a direction away from the center line of the bottom of the board. The fin body elements may be angled in a range from 2-20 degrees in some embodiments. As seen in FIG. 4, the base profile 26 of the fin body element my have a hydrodynamic foil shape. Other asymmetric shapes may be used. In some embodiments, the surface 25 of the inner face of the fin may be substantially flat. The surface 24 of the outer face 21 may have a foil profile in some embodiments. In typical usage on a surfboard, the foil profile side of the fin body element will be facing a direction away from the center line of the board.

The fins of the present invention offer many advantages. One advantage is noticeably less drag than earlier fins coupled with excellent holding of the board to the water. The reduced drag may be due to the ability of the angled tip winglets to shed vortices within the water during faster motion of the board along the water.

Another advantage of the asymmetric aspect of the fins relates to the holding power of a surfboard, with its fins, into the water, especially during turning maneuvers. During a turning maneuver, the edge of the surfboard digs in and holds an edge into the water allowing the board carve the turn. The fins further accentuate the board's ability to hold this edge for carving a turn. A fin that increases the ability of the edge of the board to remain locked into the water gives an advantage in that the board does not slip out of the water, causing either an unwanted slide out of the water, and change of direction, or a fall by the surfer. The asymmetric aspect of the fin, similar to the wing of an airfoil, will provide “lift” in that it will provide force outwards towards the edge of the surfboard. In this way, the outward force counteracts the centrifugal force of the board during turning and enhances the edge holding ability of the board.

The tip winglet may also enhance the edge holding capability of the fin and board in that the winglet may help the fin shed swirling vortexes in the fluid flow, accentuating the “lift” aspect of the fin.

Another advantage of some embodiments of the present invention is the strength of the fin. With the subtle angles of the fin body element and the tip winglet, stress concentrations are reduced. As a further enhancement of strength, in some embodiments the fin may be made of a composite material including a fabric or fiber with at least part the fabric or fiber running in continuous fashion from the fin body element to and through the tip winglet.

As evident from the above description, a wide variety of embodiments may be configured from the description given herein and additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader aspects is, therefore, not limited to the specific details and illustrative examples shown and described. Accordingly, departures from such details may be made without departing from the spirit or scope of the applicant's general invention. 

1. A fin for a surfboard comprising: a fin body element, said fin body element having a leading edge and a trailing edge, said fin element having a first side facing a first direction and a second side facing a second direction; a fin base portion, said fin base portion attached to said fin body element at a first end of said fin element; and a tip winglet, said tip winglet having a first end and a second end, said first end of said tip winglet attached to said fin body element at a second end of said fin element, said tip winglet attached at a first angle relative to said fin body element.
 2. The fin of claim 1 wherein said tip winglet is angled from said fin body element toward said first direction.
 3. The fin of claim 2 wherein said tip winglet is angled from said fin body element toward said first direction in the range of 15-60 degrees.
 4. The fin of claim 2 wherein said tip winglet is angled from said fin body toward said first direction in the range of 30-50 degrees.
 5. The fin of claim 1 wherein said fin body element has an asymmetric cross-section.
 6. The fin of claim 5 wherein said tip winglet is angled from said fin body element toward said first direction in the range of 15-60 degrees.
 7. The fin of claim 5 wherein said tip winglet is angled from said fin body toward said first direction in the range of 30-50 degrees.
 8. The fin of claim 5 wherein said fin body element is substantially flat along said second side, and wherein said first side has a foil shaped cross-section.
 9. The fin of claim 1 wherein said fin is made from a composite material comprising fibers, and wherein at least some of said fibers extend from said first end of said fin body element through to said second end of said tip winglet.
 10. The fin of claim 8 wherein said fin is made from a composite material comprising fibers, and wherein at least some of said fibers extend from said first end of said fin body element through to said second end of said tip winglet.
 11. A fin system for a surfboard, said fin system comprising a first fin and a second fin, said first fin comprising: a fin body element, said fin body element having a leading edge and a trailing edge, said fin body element having a first side facing a first direction and a second side facing a second direction; a fin base portion, said fin base portion attached to said fin body element at a first end of said fin element; a tip winglet, said tip winglet having a first end and a second end, said first end of said tip winglet attached to said fin body element at a second end of said fin body element, said tip winglet attached at a first angle relative to said fin body element; and wherein the shape of said second fin is a mirror image of said first fin.
 12. The fin of claim 11 wherein said tip winglet is angled toward said first direction.
 13. The fin of claim 12 wherein said tip winglet is angled toward said first direction in the range of 30-50 degrees.
 14. The fin of claim 11 wherein said fin body element has an asymmetric cross-section.
 15. The fin of claim 14 wherein said fin body element is substantially flat along said second side, and wherein said first side has a foil shaped cross-section.
 16. A surfboard comprising: a board element, said board having a bottom surface; and a fin system for a surfboard, said fin system comprising a first fin and a second fin, said first fin comprising: a fin body element, said fin body element having a leading edge and a trailing edge, said fin body element having a first side facing a first direction and a second side facing a second direction; a fin base portion, said fin base portion attached to said fin element at a first end of said fin body element; a tip winglet, said tip winglet having a first end and a second end, said first end of said tip winglet attached to said fin body element at a second end of said fin body element, said tip winglet attached at a first angle relative to said fin body element; and wherein the shape of said second fin is a mirror image of said first fin, and wherein said first base portion of said first fin and said second fin are attached to the bottom of said board element.
 17. The surfboard of claim 16 wherein said first fin is attached to said board element on a first side of a centerline along said bottom surface of said board element, and wherein said second fin is attached to said board element on a second side of a centerline along said bottom surface of said board element.
 18. The surfboard of claim 17 wherein said first fin body element and said second body element are angled from said bottom of said board element.
 19. The surfboard of claim 18 wherein said first fin body element and said second body element are angled from said bottom of said board element in a direction wherein in said second end of said first fin body element and said second end of said second fin body element are angled away from the centerline along the bottom surface of the board element at a second angle.
 20. The surfboard of claim 19 wherein said second angle is in the range of 2-20 degrees. 